Re: [PATCH RFC 54/77] ntb: Ensure number of MSIs on SNB is enough for the link interrupt

Jon Mason
2013-10-07T16:50:57Z

On Sat, Oct 05, 2013 at 11:43:04PM +0200, Alexander Gordeev wrote:
> On Wed, Oct 02, 2013 at 05:48:05PM -0700, Jon Mason wrote:
> > On Wed, Oct 02, 2013 at 12:49:10PM +0200, Alexander Gordeev wrote:
> > > Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
> > > ---
> > > drivers/ntb/ntb_hw.c | 2 +-
> > > 1 files changed, 1 insertions(+), 1 deletions(-)
> > >
> > > diff --git a/drivers/ntb/ntb_hw.c b/drivers/ntb/ntb_hw.c
> > > index de2062c..eccd5e5 100644
> > > --- a/drivers/ntb/ntb_hw.c
> > > +++ b/drivers/ntb/ntb_hw.c
> > > @@ -1066,7 +1066,7 @@ static int ntb_setup_msix(struct ntb_device *ndev)
> > > /* On SNB, the link interrupt is always tied to 4th vector. If
> > > * we can't get all 4, then we can't use MSI-X.
> > > */
> > > - if (ndev->hw_type != BWD_HW) {
> > > + if ((rc < SNB_MSIX_CNT) && (ndev->hw_type != BWD_HW)) {
> >
> > Nack, this check is unnecessary.
>
> If SNB can do more than SNB_MSIX_CNT MSI-Xs then this check is needed
> to enable less than maximum MSI-Xs in case the maximum was not allocated.
> Otherwise SNB will fallback to single MSI instead of multiple MSI-Xs.

Per the comment in the code snippet above, "If we can't get all 4,
then we can't use MSI-X". There is already a check to see if more
than 4 were acquired. So it's not possible to hit this. Even if it
was, don't use SNB_MSIX_CNT here (limits.msix_cnt is the preferred
variable). Also, the "()" are unnecessary.

Thanks,
Jon

> --
> Regards,
> Alexander Gordeev
> agordeev@redhat.com